Metal lubricant compositions



Patented Apr. 5, 1949 UNITED STATES PATENT OFFICE 2,466,642 METAL LUBRICANT COMPOSITIONS Robert G. Larsen, Albany, Calif., assignor to Shell Development Company, San Francisco, Calii'., a corporation of Delaware No Drawing. Application January 23, 1946, I Serial No. 642,993

11 Claims. 1

for example, as drawing operations, upsetting,

heading, die-forging, upsetting and forging machine operations, hydraulic compression systems of die-forging, forming, rolling, ironing, stamping and the like, it has been the practice to employ various lubricants to reduce wear and friction, prevent welding and metal pick-up on the forming surfaces, maintain as much as possible of the desired finish of the formed metal surface, and otherwise perform the functions of a lubricant. Metals which can be thus shaped include iron, copper, silver, aluminum, magnesium, as well as the alloys of these and like metals.

Hetertofore, petroleum oils as well as vegetable oils, such as palm oil and peanut oil, have been used for such purposes. However, metal lubricants containing or consisting of such oils inherently possess certain defects. Thus, they are unstable under the conditions of use and will decompose or at least quickly lose their initial lubricating action. Along with the progressive decomposition of mineral oils and vegetable oils when used as lubricants per se or with many-common additives (such as friction-reducing agents and known antiwear agents), in severe cases of use, there occurs a charring and even (in some cases) a flashing. On account of deficient lubrication of local areas between the surfaces of a die and the metal being shaped, welding, furrowing, cutting of lines, and scratching of the metal surfaces known as scoring have also occurred. Also, due to faulty lubrication and decomposition of the starting lubricant compositions, undesirable deposition of constituents and decomposition products of the lubricant composition, has been frequently noted. Good lubrication is in part the effective prevention of contact of two metal surfaces by means of an oleaginous film, but in cases of faulty lubrication the metal surfaces are allowed to come together, and under the effect of heat and pressure these metal surfaces become welded. The addition of various finely divided materials, commonly called fillers,

position markedly, but at the same time such compositions are unsatisfactory in that scoring to mineral oil and vegetable oil lubricants to prevent marked decomposition of these oils, to prevent scoring, pick-up and welding has generally not been satisfactory. For example, the addition of kaolin as a filler to ordinary lubricant oils has been found to reduce charring and decomis bad and pick-up severe. Additionally, the known lubricants have been found unsatisfactory in the die-forging and drawing of magnesium alloys, of aluminum alloys, and of aluminum coated sheets, which are advantageously shaped at temperaturs above 400 F., e. g. from about 400 F. to 900 F., or even higher.

It is therefore an object of the present invention to provide novel lubricant compositions which obviate the above and other defects. Another object is to provide new lubricant compositions which have superior stability under the conditions of heat and pressure. A further object of this invention is to provide a metal lubricant which is particularly suitable for use during the shaping end/or drawing of aluminum alloys, ma nesium alloys, and aluminum coated sheet material into objects essentially free of undesirable deposits and practically free of scoring.

It has now been discovered that compositions consisting of, comprising or containing an antiwelding agent and an associated or polymerized silicon-containing organic compound having the general structural formula:

(-SF-O) Silicone, or (A|i0) Meta silicate i KR wherein each R is a hydrocarbon radical of less than 20 carbon atoms, or their substituted derivatives, each X is an atom selected from the group consisting of oxygen, sulfur, selenium and tellurium, and n is a positive integer of at least 2, are outstanding lubricants which accomplish the foregoing and other objects. The hydrocarbon radical R of the above formulas may be an alkyl, alkenyl, aralkyl, alkaryl, or a heterocyclic group, but is preferably a straight chain or a cycloaliphatic radical. The following are illustrative examples of such hydrocarbon radicals: methyl, ethyl, n-propyl, isopropyl, the various butyl, amyl, hexyl, heptyl, octyl, nonyl, decyl, and higher radicals, as well as cyclic groups such as phenyl, benzyl, tolyl, naphthyl, cyclopentyl, cyclohexyl, terpenic groups such as bornyl, fenchyl, and the like, and their homologs and analogs. These radicals may also contain such substituents as esterified sulfonic, alkoxy, nitro, halogen, and similar substituents which do not interfere with the beneficial use of the compounds.

It has been further discovered that compositions consisting of. comprising or containing laminated or foliated solids in a finely divided 8 condition and an associated or polymerized silicon-containing organic compound having the general structural formula sitions which are also eminently suitable for the desired purpose. Compounds containing low molecular weight alkyl radicals tend to be more highly polymerized. Dicetyl silicone, on the other hand, seems to form an association of about three monomeric units.

The following are illustrative examples of laminated foliated solid components which may be eifectively used together with the abovedeiined associated silicones or silicates: graphite, talc, vermiculite, tungsten disuliide, molybdenum disulflde, zinc oxide, calcium oxide, mica, silver sulfate, lead iodide, and the like. Compositions containing graphite incorporated in polymeric dimethyl silicone (or the like) should preferably contain graphite in an amount of from about 1% to about 25% by weight of the composition, the preferred graphite content being between about 10% and about 20% by weight of the total composition.

Compositions containing the above ingredients are not only superior lubricants, but they also possess superior stability under the conditions of heat and pressure. One of the most outstanding discoveries of the present invention is the finding that compositions of an anti-welding agent and of an associated or polymerized oxy-silicon organic compound of the class described herein are highly satisfactory as primary lubricants. Thus, it was found that such combinations or compositions form a satisfactory film between two moving surfaces, reduce the coeflicient of friction, and prevent wear anddistortion of the die or worked metal surface. When attempts are made to use polymeric dimethyl silicone, or like associated silicones or silicates, alone as a lubricant at temperatures of above about 200 F. and pressures of the order of 1500 to 100,000 p. s. i., the frictional force developed is too high to permit practical usage and objectionable pick-up occurs on the die or working metal surfaces. At the same time, in some cases as at about 700 F., part of the lubricant decomposes and either flashes or chars, or both.' However, when between about 10% and about 20% by weight of graphite is incorporated into the polymeric dimethyl silicone, this combination lubricates satisfactorily, the die or metal working surfaces being essentially free of deposit, and the frietional force remains lower than that obtained when either the polymeric dimethyl silicone or the graphite is used individually.

Dispersions of polymerized dimethyl silicone and graphite in normally liquid hydrocarbons. such as polyisobutylene, are also of further utility in that practically all of the advantages of the two-component composition (silicone and graphite) are obtained even though employing the liquid hydrocarbon as a diluent. serves to replace a part of the polymeric dimethyl silicone, with the resultant saving in cost. However, it is essential to use a predominant amount of the associated or polymerized silicon-containing compound of the above-described class. Thus, the use of these three-component lubricant compositions results in less scoring and less deposit than when a composition of graphite together with polyisobutylene is used without incorporation of the polymeric dimethyl silicone or of a like silicon-containing compound of the defined class. Usually, a maximum of about 25% of a high-boiling liquid hydrocarbon lubricant in the described compositions containing a silicon-containing organic polymer and graphite should not be exceeded. Aside from a diluent effect of a hydrocarbon liquid, as employed in the present compositions. the hydrocarbon can also be used as an aid in spreading such compositions on a metal surface. An adhesive eifect may also be obtained when a viscous mineral oil or asphalt is employed in the compositions of the present invention. One may employ a viscous oil such as a mineral oil having a Sayboit Universal viscosity at 210' I". of up to about to seconds, or higher, without the necessity of using any corrosive extreme pressure agents, e. g. sulfur, phosphorus, and halogen containing extreme pressure additives. In fact, it is preferable to omit the latter in order to obtain noncorrosiveness along with high iilm strength. Such hydrocarbon lubricants may be substituted in whole or in part by fatty oils of animal or vegetable origin such as castor oil, palm oil, peanut oil, and similar oils as well as by the so-called synthetic lubricants produced, for example, by the I polymerization of oleflns, various unsaturated compounds, esters, ethers, and similarly polymerizabie compounds. In contrast, when peanut oil was tested alone as a lubricant in the drawing of aluminum alloy 5280, this oil decomposed during the drawing operation to the extent that pick-up was severe and flashing and charring occurred. But up to 20% of the total present compositions may consist of peanut oil, in which case the freedom from pick-up and freedom from charring is practically the same as when no peanut oil is used. Also, mixtures containing polymeric dimethyl silicone, graphite, peanut oil, and polyisobutylene may be used.

Lubricant compositions of the present invention possess further advantages in that the various known additives, for example the usual antiwear, friction-reducing, viscosity-improving and stabilization agents need not necessarily be added thereto. However, these various materials maybe added to the compositions of this invention without departing from the scope and spirit of the invention described herein. In general, the polymeric organic silicones and silicates, together with a laminated foliated solid in a finely divided condition, may be used either as such or in combination with other partially eiiicacious or .practically inert substances, and applied to various surfaces for the purpose of lubricating them. It will be appreciated that the description herein of the use of the described compositions The latter as lubricants is given by way of illustration only and that the invention is not limited to" the employment of, for example, such polymeric oxysilicon organic compounds together with graphite, or with talc or the like, for purposes of lubrication of roller bearing surfaces, or during die-forging, or drawing of metals; sincethe compositions of this invention are broadly applicable as lubricants wherever a lubricating problem occurs.

In some cases it is advantageous to have present both a polymerized oxy-silicon organic compound having short alkyl radicals such as polymerized dimethyl silicone and also a like compound having long alkyl radicals such as an associated polymerized dicetyl silicone.

The oxy-silicon organic polymers which are used as an ingredient or ingredients in the pres- The preparation of polymeric dimethyl silicone is described in 63 J. A. C. S. 798 (1941). Mixtures of such silicon halides containing different alkyl radicals and/or different halogen radicals may likewise be hydrolyzed to yield (in the case of silicon halides containing different alkyl radicals) mixed silicones, that is, compounds wherein the two organic groups are dissimilar.

As an example, dicetyl silicone was prepared as follows: A solution of 158 g. (0.507 mols) oi cetyl bromide in ether was added to 12.3 g. (0.507 mols) of magnesium turnings covered by ether containing a trace of iodine, and the mixture was refluxed. The resulting cetyl magnesium bromde solution was added to an ethereal solution of,

42 g. (0.247 mols) of silicon tetrachloride. The Grignard addition product precipitated out at room temperature but was soluble in ether at C. to C. It was hydrolyzed with cold,

dilute sulfuric acid and the ether layer evap-,

further purification was 63 C. to 65 C. An

ebullioscopic determination of the molecular weight of dicetyl silicone in methyl ethyl ketone solution indicated a molecular weight of approximately 1500, indicating that the dicetyl silicone was associated or polymerized to the extent of three monomeric units.

The meta silicates may be prepared by reacting the desired alcohol, mercaptan. selenol or tellurol (or mixtures thereof) with silicon tetrachloride and water in the proportions The ingredients may be maintained anywhere from room temperature up to about 350 C. or more when refluxing, or otherwise up to about the boiling temperature of the alcohol or analogous compound, until the reaction is substantially complete. The reaction may be eflected either without the use of a diluent, or in the presence of an inert solvent for the reactants such The yield was 93 got-- as water, dioxane, etc. Reaction time ison the order of a few hours to a day.

The ortho silicates may be obtained by ester exchange reaction with tetra ethyl ortho silicate [(021150) 481], a commercial product. Tetra methyl ortho silicate may likewise be used; such compounds can be obtained by reaction of SiCli with anhydrous alcohol. The ester exchangereaction is effected by heating the desired alcohol, mercaptan, selenol or tellurol (or mixtures thereof) with the ortho silicate. The synthesis is conveniently effected in the presence of anhydrous acid orbasic catalyst such as benzene sulfonic acid, para-tolnene-sulfonic acid, sodium 'ethoxide, etc. During this ester exchange reaction, a suitable temperature range is above the boiling point of ethyl alcohol (which is driven off from the ortho silicate) ,up to about 200 0., a preferred range being about C. to 150C. If desired, suflicient toluene or other solvent may be added so as to form an azeotrope with the ethyl alcohol produced. Reaction time is 2 to 3 hours or more depending on the efliciency of the ethyl alcohol removal.

Association or polymerization of the silicon oxides and esters may be promoted, if desired, by heating in the presence of oxygen with an acidic agent such as HCl, H2SO4, H3PO4, HF, BFa, Bra, etc. For example, the degree of polymerization of dlmethyl silicone was very considerably increased by refluxing it with a few drops of concentrated hydrochloric acid at C. to 138 C. for about 16 hours. For compounds of greater monomeric molecular weight a temperature in the range of about 175 C. to 250 C. is usually applicable for a period ranging from a few hours to several days. The ortho silicates can be polymerized by simply exposing them to water vapor. The term associated compound as used herein and in the appended claims is taken to include both the highly polymerized and the loosely as-- sociated compounds.

Silicones in which the two Rs have different values were made by adding mixtures of two or more organo-magnesium bromides (for example dodecyl magnesium bromide, eicosyl magnesium bromide, etc.) to the silicon tetrachloride and :hydrolyzing the product as in the foregoing example.

A number of materials comprising the present invention were tested in a four ball machine sim- ,July 14, 1933.: This apparatus comprises a series of four steel balls arranged in pyramid formation. The top ball is rotated by a spindle against the three bottom balls which are clamped in a stationary ball holder. The balls are immersed in the lubricant to be tested. Tests were run for two hours at 700 R. P. M. under a '7 kg. load and at a controlled temperature of C. The diameters of the wear scars worn on the three balls forming the base of the pyramid were then measured, and the average taken as the true indication of. wear. Results were as follows:

As seen from the above table, the described polymerimdsiliconesmaybeusedaslubricants by themselves under such relatively mild conditions as at an order of temperature of about 150 C. But in lubricating operations, more particularly those occurring in metal-shaping processes above about 400' 1"., the polymeric silicones by themselves suffer from various combinations of the defects described previously herein. In accordance with the present invention. a superior lubricant composition is obtained by the incorporation of minor amounts of a laminated foliated nnely divided solid, such as powdered graphite, into an associated or polymerised silicon-containing organic compound of the defined class. The laminated foliated finely divided material acts as an antiwelding agent.

As an illustrative example of the exceptional suitability of the novel compomtions as lubricants, an aluminum alloy was coated with polymerized dimethyl silicone containing 10% graphite and then drawn into a cupped shape at about 800' 1". with practical and satisfactory results. Compared with other lubricants, only a low drawing force was required and the shaped metal emerged u with a clean surface. Good lubrication by the composition wm shown by the fact that there was an absence of scoring, pick-up, and welding. These results were in contradistinction to the usual cases with previous lubricants where a sticking or welding to the die of the object being formed has made the operation impractical. stability of the present novel compositions was at a practical maximum measured in terms of the satisfactory lubrication in this drawing operation and the fact that although some smoking occurred at 800 F. during the drawing, no decomposition suiilcient to be detrimental to the lubricating action could be observed. The present compositions can also be employed satisfactorily for the ordinary lubrication of moving metal surfaces, as for example ball bearings, the suitability of which lubricants are tested in the four ball machine described in the magazine Engineering, vol. 136, July 14, 1938.

As another example, a composition comprising, by weight of graphite, from about 80% to 70% by weight of polymerized dimethyl silicone and between about 10% and 20% by weight of a hydrocarbon, e. g. polyisobutylene, when employed as a lubricant in the drawing of an aluminum alloy results in the obtaining of highly satisfactory results.

The present application is a continuation-inpart of the copending application Serial No. 554,- 723, flied September 18, 1944.

I claim as my invention:

1. A lubricating composition consisting essen-- tially of a major amount of a mixture of dimethyl silicone and dicetyl silicone, between about 1% and about graphite and a minor amount of less than 25% of polyisobutylene.

2. A lubricating composition consisting essentially of a major amount of di-n-propyl silicone, between about 1% and about 25% graphite and a minor amount of less than 25% of polyisobutylene.

3. A lubricating composition consisting essentially of a major amount of dimethyl silicone, between about 1% and about 25% graphite and a minor amount of about 10% and of less than 25% of polyisobutylene.

4. A lubricating composition consisting essentially of a major amount of dimethyl silicone,

8 between about 1% and about 25% m disulilde, andaminoramountoflesstban25$ of polyisobutylene.

5. A lubricating composition consisting essentially of a major amount of di-n-propyl silicime, between about 1% and about 25% molybdenum disulfide and a minor amount of less than 25% of polyisobutylene.

5. A lubricating composition consisting essentially of a major amount of a mixture of dimethyl silicone and dicetyl silicone, between about 1% and about 25% molybdenum disuliide and a minor amount of less than 25% of polyisobutylene.

7. A lubricating composition consisting essentially of from 1% to 25% of a laminated foliated nnely divided antiscoring agent from the class consisting of graphite, molybdenum disulnde, vermiculite, talc, tungsten disulflde, zinc oxide, calcium oxide, mica. silver sulfate, and lead iodide; from 10 to 25% polyisobutylene, and the balance being a polymeric organic silicon-containing compound having the general structural formula of the group consisting of (.31...) (ii) i in and mixtures thereof wherein each R is selected from the group consisting of unsubstituted and substituted hydrocarbon radicals having less than 20 carbon atoms, each X is an atom selected from the group consisting of oxy en, sulfur, selenium and tellurium, and n is a positive integer of at least 2.

8. A lubricating composition consisting essentially of from 1% to 25% of a laminated foliabd fully divided antiscoring agent from the class consisting of graphite, molybdenum disulflde, vermiculite, talc, tungsten disulilde, zinc oxide, calcium oxide, mica, silver sulfate, and lead iodide: from 10 to 25% polyisobutylene, and the balance being a polymeric dialkyl silicone.

9. A lubricating composition consisting essentially of 1% to 25% of graphite; 10 to 25% P 17- isobutylene, and the balance being a normally liquid associated dialkyl silicone.

10. A lubricating composition consisting essentially of 1% to 25% molybdenum disuliide; 10 to 25% polyisobutylene, and the balance being a normally liquid associated dialkyl silicone.

11. A lubricating composition consisting essentially of 1% to 25% vermiculite; 10 to 25% polyisobutylene, and the balance being a normally liquid associated dialkyl silicone.

ROBERT G. LARSEN.

REFERENCE CITED The following references are of record in the his of this patent:

' UNITED STATES PATENTS Number Name Date 2,090,263 Moses Aug. 17, 1937 2,258,218 Rochow Oct, 7, 1941 2,356,387 Wright Aug. 22, 1944 2,375,007 Larsen May 1, 1945 2,384,384 McGregor Sept. 4, 1945 2,398,187 McGregor Apr. 9, 1945 2,413,582 Rust Dec. 31, 1945 OTHER RH'ERENCEB Chem. 81 Engineering News, Apr. 10, 1945, page 5.

Certificate of Correction Patent N 0. 2,466,642. April 5, 1949. ROBERT G. LARSEN It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 3, for that portion of the first formula reading column 8, line 37, claim 8, for the word, fully readfinely; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of November, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gommz'ssioner of Patents. 

